You might not use a cross laser often, but it's very handy to have your own once the need arises. There's no cord to restrict you, just make sure you've charged the battery.
It's a good time to buy! Prices are currently £72 less than average.
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Dewalt DCE088NG18 Cross Line Green Beam Laser 12v 18V Bare + Case DCE088NG18-XJ